The aim of the experiments described in this proposal is to study the relevance of gs antigen to prostatic cancer in humans. In initial studies, radioimmunoassay for gs-3 antigen will be standardized. This assay will be employed to detect and quantify gs-3 antigen in normal, hyperplastic, and malignant prostates. The data will be analysed for any correlation between the quantity of antigen and clinical disease. Concurrently, we will use the radioimmunoassay to detect gs antigen in the mouse prostate. If the antigen is detectable, the effect of hormone treatment on the amount of gs antigen in the mouse prostate will be evaluated.